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I'm using vpnc for a VPN client. I'm also doing some tricky things with route to make sure I can still access my local network, etc. etc. (the particulars here are not very important).

Sometimes I get the routing table so jacked up I get ping: sendto: Network is unreachable for urls that should otherwise resolve.

Currently, if I restart Mac OS X then everything is back to normal. What I'd like to do is reset the routing tables to the "default" (e.g. what it is set to at boot) without a whole system reboot.

I think that step 1 is route flush (to remove all routes). And step 2 needs to reload all of the default routes.

Any thoughts on how to do this? (e.g. what is step 2?)

EDIT Also, I'm noticing another symptom is traceroute also fails on the address in question. For instance:

traceroute the.good.dns.name

traceroute: bind: Can't assign requested address

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3 Answers 3

up vote 23 down vote accepted

You need to flush the routes . Use route -n flush several times . Afterwards add your routes with route add.

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I've changed this to the accepted answer. It works! I did route -n flush several times, then I just restarted my networking via the System preferences. It only took me a year to come back and figure this out :) –  Nate Murray May 13 '11 at 16:44
This solved a similar problem for me with the Sonicwall's Aventail Connect VPN client which I find particularly prone to "Can't assign requested address" failures, especially when switching wireless networks. Now I have a way to resolve that doesn't avoid a power cycle. Thanks! –  Alan Donnelly Oct 18 '12 at 18:56

First you need a route for your network interface. If the VPN is disconnected then just take your network interface down and then bring it back up with ifconfig. Then use the route commnand to build in your default gw. So something like:

ifconfig en0 down

ifconfig en0 up

route add <ip address> default

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Yes, but how does Mac OS X know what the default route's ip address is? What I'd really like to see is how Mac OS X does the boot process and do the exact same thing. –  Nate Murray Oct 26 '09 at 22:10
...? It gets it from DHCP... –  Jordan Eunson Oct 26 '09 at 22:21

I was running into this issue while using a home OpenVPN server and connecting to it using the Tunnelblick application on Mac.

What was happening on my end is that a route with my home IP as the destination and an incorrect gateway was getting leftover after disconnecting from the VPN. Deleting this route solved the issue, simply

$ sudo route -n delete the.good.dns.name

Example: I am at school and after a fresh computer boot, I connect to a wireless network. I connect to my home OpenVPN server with Tunnelblick.

$ netstat -nr
Destination                   Gateway
[home-ip]/32                  [school-default-gateway-1] ....

I disconnect from the VPN server. I change wireless networks. This changes my default gateway.

$ netstat -nr
Destination                   Gateway
[home-ip]/32                  [school-default-gateway-1] ...
$ ping [home-ip]
PING [home-ip]: 56 data bytes
ping: sendto: Network is unreachable
ping: sendto: Network is unreachable
Request timeout for icmp_seq 0

I can't under any circumstances connect to my home network (VPN, ping, anything) after this happens. If I then just delete the route:

$ sudo route -n delete [home-ip]
delete net [home-ip]
$ ping [home-ip]
PING [home-ip]: 56 data bytes
64 bytes from [home-ip]: icmp_seq=1 ttl=56 time=13.111 ms

It works fine.

There might be an issue with how the OpenVPN server/client is configured which is leaving this (and I'd be interested in finding out what that is), but I installed a Tunnelblick post-disconnect script that automates this route deletion.

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I'm actually having a similar issue here. Really annoying. –  Tom Busby Jun 17 at 14:16

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